[boost] C++0x configuration macros redux

Hi all, A while back, I put some preliminary C++0x configuration macros into the Config library, but they were half-baked. I've finally finished them. The macros are: BOOST_HAS_CONCEPTS BOOST_HAS_LONG_LONG (it's part of C++0x) BOOST_HAS_RVALUE_REFS BOOST_HAS_STATIC_ASSERT BOOST_HAS_VARIADIC_TMPL Documentation, configure tests, and the appropriate detection code is on mainline CVS. The only client of these macros so far is static_assert.hpp, which uses the C++0x static_assert facility when it is available. In the near future, I hope to get some nightly regression tests running with the prerelease GCC 4.3's experimental C++0x mode, so we can start trying out some of these features in Boost. Cheers, Doug